When our 2000 EB Expy is parked, the air suspension lets the right side down lower than the left side. It makes it look as if we have a flat tire. Any ideas as to why this may be? When we're driving it seems level, it's just when it's parked...

 

You may be able to correct that by adjusting the torsion bar. Do it conservatively, turning one side half turn at a time and then observe (use a level). It depends on which one you prefer to adjust, you may want to raise the sagging side by turning the torsion bar on that side clockwise (harder), or the higher side by adjusting counter-clockwise (easier). Use WD40 liberally before doing the adjustment, and if you opt for the latter, you may not need to raise your truck. Of course, its ideal to relieve some tension to the bar by jacking the truck up. Based on my experience, when I lowered my truck, its not necessary to jack up the truck, but I must emphasized that I did the counter-clockwise adjustment on both sides.

Please be careful and turn off the air suspension switch on the passenger side kick panel area before going under your truck.

One more note: I observed that with LLS, the truck is somewhat 'sensitive' to uneven pavement, such that when parked on one, the 'lean' of the truck is more than what the pavement's grade, giving one that feeling that the truck is not level.

Also, the eye can sometimes deceive, I swear I thought my truck leans on the driver side but in fact is slightly lower on the other side when I used a level. Of course, my method of observation is hardly scientific. And finding a perfectly level paved ground is another challenge.

BTW, my opinion on this matter is based on the fact that I once owned a conventional suspension expedition and didn't have the same issue or observed anything like this.

Good luck